Electrical resistance device



Feb. 4, EQSQQ A. s. HOWELL 1,745,487

ELECTRICAL RES ISTANCE DEVICE Filed Aug. 17, 1928 3 Sheets-Sheet l hwfiw @4662"? A. 50%2 1/ axis.

Feb. 4, 130 A. s. HOWELL 1,745,487

ELECTRICAL RESISTANCE DEVICE Filed Aug. 17; 1928 s sheets-sheet 2 Feb. 4, 1930 A. s. HOWELL 11,745,487

ELECTRICAL RES ISTANCE DEVICE Filed Aug. 17, 1928 3 Sheets-Sheet 3 Patented Feb. 4, 1930 UNITED STATES PATENT? OFFICE ALBERT S. HOWELL, OF CHICAGO, ILLINOIS, ASSIGNOB TO THE BELL 8t HOWIIIL COM- PART, OF CHICAGO, ILLINOIS, A. COBFOBATION F ILLINDIS ELECTRICAL RESISTANCE DEVICE Application filed August 17, 1928. Serial No. 300,230.

My invention relates particularly to an electrical resistance device for motion picture projecting machines, although not limited to this use alone.

The general objects of my invention reside in the provision of a simple, effective and compact electrical resistance device, which is preferably variable, and which is particularly adapted to the motion picture projecting machine described and claimed in U. S. Letters Patent, No. 1,587,955, granted June 8,

1926, for improvement in motion picture proj ecting machine and the like.

With these objects in view my invention consists in certain features of novelty in the construction, combination and arrangement of parts by which the said objects and certain other objects, hereinafter appearing, are

eifected, all as fully described with reference to the accompanying drawings and more particularly pointed out in the appended claims.

in the said drawings Figure 1 is a side elevation of a motion picture projecting machine embodying my invention;

Figure 2 is an enlarged partial vertical section of the lamp chamber of the machine;

Figure 3 is a section on the line 33 of Figure 2;

Figure 4 is a view of the resistance assembly of the device, hereinafter described;

Figure 5 is face view of one of the anchors of the resistance assembly laid out flat.

Figure 6 is an enlarged partial section on the line 66 of Figure 7 and Figure 7 is a top plan view of the resistance of my invention.

Like characters of reference indicate like parts in the several views.

Referring to the drawings, 1 designates a base which supports a mechanism frame 2, and this frame includes a lamp chamber 3 within which is disposed an incandescent electric lamp 4. to provide the projection light. See Figures 1 and 2.

During operation of the machine an air current is forced upwardly through the lamp chamber to dissipate the heat of the lamp and the resistance device of my invention which is disposed above the lamp and forms the top of the lamp chamber.

This resistance device includes a body part of insulating material, such as porcelain, which comprises a cylindrical wall 5 corresponding with the diameter of the lamp chamber and a transverse wall 6 disposed intermediately of the ends of the cylindrical wall. See Figures 1, 2, 3 and 7. The body part is secured to the lamp chamber by means of headed screws, not shown, passing down-' -wardl through diametrically opposite apertures in the body part and screwthreaded into the Wall of the lamp chamber.

The transverse wall 6 of the body part is perforated, as designated at 8 in Figures 3 and 7, for the passage of air therethrough, and metal anchors, generally indicated at 9, are spaced about the axis of the body part on the lower face of the transverse wall 6 adjacent the cylindrical wall 5. See F igures' 2, 3, 4, 5 and 'Z. These anchors have'portions 11 engaged against the lower face of the transverse wall 6, and headed screws 12 pass downwardly through apertures in said transverse wall and are screwthreaded into the portions 11 of the anchors to secure the same to the body part. See particularly Figures 2 and 3.

The anchors 9 have portions 13 extending from the portions 11 adjacent the cylindrical wall 5 away from the transverse wall 6 and toward the axis of the body part, and these portions 13 are provided adjacent their outer ends with stud formations 14 and bendable ears 15 adjacent thereto, as best shown in Figure 5.

The resist-ance element of the device consists of a coiled resistance wire 16 of suitable metal,.such as nichrome resistance wire, and this coiled resistance wire is secured at in- 99 tervals therealong to the anchors 9 by means of coils 17 thereof, see Figures 4 and 5, be-

ing engaged on the stud formations 14 and the ears 15 being bent-thereover to secure the coils 17 on the stud formations 14.

The resistance wire 16 has looped sections, 18 between the anchors 9 which project therefrom downwardly away from the transverse wall 6 and toward the axis of the body part, thus suspending the resistance wire in the path of the air current in the lamp chamber which flows upwardly therein about the lamp and through the perforations 8 through the transverse wall 6. See Figure 2.

It will be observed that the resistance wire 16 may be assembled with the anchors9, as shown in Figure 4, and then be secured in the body part by means of the screws 12.

In order to effect a variation of the resistance of the unit the following is provided.

Engaged in an axial aperturethrough the transverse wall 6 is a flanged metal bushing 19 which is securedwith the transverse wall by means of headed screws 21 passing down wardly through apertures in the transverse wall 6 and screwthreaded into the flange of the bushing. See Figures 2 and 6.

Rotatably mounted in this bushing is a metal stud 22 on the lower end of which is secured a spring metal contact arm 23 which is disposed at the under face of the transverse wall 6 and is adapted in its pivotalinovement with the stud 22 to selectively contact the portions 11 of one half of the anchors 9, bosses 24 formed on the inside of the cylindrical wall 5 of the body part about the apertures 7 limiting the movement of the contact arm to this extent. See Figures 2, 3 and 6.

Secured on the upper end of the stud 22 is an operating arm 25 which is disposed at the upper face of the transverse wall 6 and which is laterally enclosed against accidental movement by the portion of the cylindrical wall 5 above the transverse wall 6. See Figures 2, 6 and 7. Thus the contact arm 23 may be conveniently adjusted from the exterior of the lamp chamber.

A metal strap 26 is clamped between the flange of the bushing 19 and the underside of the transverse wall 6, and extends to a terminal 27 on the inside of the lower portion of the cylindrical wall-5 whereby the contact arm 23 is connected in circuit, see Figure 2, and one end of the resistance wire is connected in circuit in a similar manner.

The looped sections 8 of the resistance wire 16 between the anchors 9 which are contacted by the arm 23 are relatively short, as shown in Figure 4, in order that the difference in resistance between these anchors is correspondingl small.

While I have described and shown the preferred embodiment of my invention I do not wish to be limited to the precise details of construction as changes may readily be made without departing from the spirit of my invention, but having thus described my invention, I claim as new and desire to secure by Letters Patent the following:

1. In an electrical resistance device the combination with a body part of insulating material having a wall perforated for the passage of air therethrough, of a plurality of metalanchors spaced about an axis disposed centrally of said wall and provided with stud formations and bendable ears adjacent thereto, headed screws passing through apertures in said body part and screw-threaded into said anchors to secure the same to said body part, and a coiled resistance wire secured at intervals therealong to said anchors by means of coils thereof being enga ed on said stud formations and said ears, eing bent thereover, said wire having looped sections between said anchors and projecting therefrom toward said axis.

2. In an electrical resistance device the combination with a body part of insulating material comprising a cylindrical wall and a transverse wall disposed intermediately of the ends of the cylindrical wall, said transverse wall being perforated for the passage of air therethrough, of a plurality of metal anchors secured against one face of said transverse wall and spaced about the axis of the bed part and disposed adjacent the cylindrica wall, coiled resistance wiresecured at intervals therealong to said anchors and having looped sections between said anchors and projecting therefrom, a contact arm-disposed at said face of said transverse wall and pivotally mounted on this wall for movement on the axis of the body part for selective contact with said anchors, and an operating arm on the other face of said transverse wall and operatively connected with said contact arm.

3. In an electrical resistance device the combination-with a body part of insulating material comprising a cylindrical wall and a transverse wall disposed intermediately of the ends of the cylindrical wall, said transverse wall being perforated for the passage of air therethrough, of a plurality of metal anchors spaced about the axis of the body part and disposed adjacent the cylindrical wall and having portions engaged against a face of said transverse wall and other portions extending from these portions adjacent said cymeme? face of the transverse wall and pivotally mounted thereon on said. axis for movement for selective contact with the first mentioned portions of said anchors, and an operating arm on the other face of said transverse wall and operatively connected with said contact arm.

In Witness whereof I hereunto afix my signature this thirteenth day of August, 1928. ALBERT S. HULL. 

